Polarity indicator



Dec- 9, 1952 A. E. ANDERssoN PoLARfry INDICATOR Filed Nov. l0, 1948.devi-Em Q IN V EN TOR. me ANnEressoN ANDERS Em Patented ec. 9, 1952UNITED STATES RTEN T OFFICE ,Anders vEinar Andersson, .Minneapol-is,Minn.

ApplicationrNovember 10, 1948, Serial No.159;251

.2 Claims.

Myinvention relates to .an improved .polarity indicator .for.determining :the polarity of -electromagnetic elds.

As .is .well known, felectric machinesaoftheggeneralclass of:mctors.and'fgeneratcrs have .as an .essential part of vtheir operating`.mechanism ,-a .number of .electrical windings Aused to :produceelectromagnetic .force In .various ,-.arrangementa these windings aredisposed .about lacentral Aaxis of 1a part of Ythemachine, and tobaefectvely disposed, those windings which .produce :a p ositiveVelectroniotive ,force :must be alternately dis-.posedwithrelationitothosewhich.produceagnegatve .electromotive force1in assembling :machinesrof thisrtype..:.themechanicnr operator who isengaged `in the assembling ,operation cannot .distinguish the positiveand .negative :windings merely Yby utheir :appearance .and 1 must,therefore, relyonsomeothermeans to determi-nethepolarityof each of .the.elementafas,otherwise thepasrts are fapt to be assembled in.suchgaimanner as lLto render the machine inoperative.

.There have b eenvseveral `known devices Yfor :indicating polarity.-OreIeCt-IOmagnetic `elds, .some ofi-which are .relatively Acomplexland require vsome form rof manual manipulation. The most commonlyacceptedysimple indicating device has been la magnetic-compass. The useof\acompass,;how ever, canbecome unsatisfactory after 'a certain amount-of use because the magnetism of :the needle can be materially affectedhykthemagnetic effect of the eldsso that it is v-no longer-dependalole.-

I have discovered a relatively simple 1dev ice Afor determiningthedpolarity offelectromagneticgields, which is certain in operation`and which r.does notrequireany form of manual manipulationof theyindicating mechanism. The v present Ainvention includes as `.anessential element an yarmature .mounted within a casing and supported bybearing means which .will permit its .free axial movement. Thecasing.has connected 4thereto :a rigid ,conductor inthe form cfa steel rodwhich maybe placed in contact with .an electromagnetic field .to form a.conducting path from the eld to the armature so as vto attractVor-repel one end of the ,armature vthereby causing ^the armature torotate on its bearing Support. In order to stabilize the armatureagainstuncontrolled movement and tu further maintain well establishedmagnetic'poles-at theopposite ends ofthe armature, one or more permanentmagnets are --contained within the Vcasi-ng with their oppositepolesspacedfrom eitherend of the armature so that thearmature is alwayswithin -the magnetic-path between the opposite poles of the magnet. Anindicating needle is secured to the armature or its bearing support, andthis .needle is movable with `respectto ya printed index carried by thecasing `and havingindiciathereonto indicate the (ci. ris-.183)

positive :and :negative =poles, :to one of -which the needle :will 'bemoved pwhen the aforementioned .rod is brought -infclose vproximityto-an electroymagneticeld. .Spring means aregsecured to the bearingsupport lfor the armatureandrthegindileating .fneedle, lto ,return v theneedle vvto ,3a neutnal position when v.the device is inactive.

.An important advantage of rthe invention nds that a Vunitary structureis providedwhich does not require manual manipulation. Moreover, Atheindicating needle does not -wobble'in luncontrolled movement -as in theinstance l of a -imagnetic compass since `the armature is vconstantlysubject to the lines of magnetic f force i passing from ;the ep posite:poles lof the 'adjacent v--permanent mag-net. Furthermorathe nehairspringralsof-acts :tosta- .bilize .thearmature against uncontrolled.mo-Vement f and .to vfiImmediately 'return .it t to 1a neutralposition.

-An objectof .the .invention isf-to provide a relatively simple,andeiective device .for indicating the polarity lof ,anelectromagnetic-i-leld.

Another Objectis toprovide a `polarity indica.- tOr which includesacasingcontaining an arma.- ture supported for .axial rotation, which.armature is mounted Within the casing on ,onesideof the centralA axisthereof, andarigid rod-secured to a side ofthe ycasing nearest thearmature Afojr conducting magnetic flux from .an .electromagnetic neldioAthe casing 'in such a manneras'to attract one end ofthe armature,Atogether vWith indicating mean-s cooperab'le with the armature forindicating the polarity yojf 'the electromagnetic el'd.

A further object isto'provide apolarity `indicator whichincludes anarmature formed of substantially rectangular configuration whichissupported within a casing vadjacent vone-side thereof by means whichwillperm-it v-free-axia1'mover-nent of the armature, together `with-ametallic nccnductor secured '-to the-casing -and adapted Ltofferm apath for magnetic flux froman electromagnetic iield to the casing toattract one-end of the armature, and a permanent magnet positionedWithin the casingand having its opposite vpoles -spacedfon either sideof the armature so that the armature is positioned in themagnetic eldofthe magnet and is stabilized by the magnet.

Other and fur-theriob'jects may becomeappar.- rent from the .followingdescription and claims., and in the appended drawing in-wliich':

t Fig. 1 is a general exterior view oftheinveni lon;

Fig. 2 is a section Itaken on the lines 12-2 of Fig. 3, showing on.anenlargediscale.theinterior of a portion of vthe .device shown finFig.Yl;

Fig. 3 is an enlarged vertical section itakenion thelines v3 3 of Figu2;and,

Fig. e shows the manner in 4which-the vinvention is applied .to anelectromagneticeld ofi'a'n 3 electric machine for determining polarityof the field.

Referring now to the several views of the drawing, general referencenumeral I indicates a polarity indicator and includes a casing I2 ofcylindrical configuration which, as indicated in Fig. 3, is hollow andis enclosed on its forward face by a transparent window I4.

As best shown in Fig. 3, within the interior of casing I2 is an innercasing i6 which is clamped to the forward edge of casing I2 by a ringI8. As seen in Figs. 2 and 3, a plate 20 is secured to casing I6 by anut and bolt arrangement 22. Plate 2D has a tapered extension 24whichterminates in an upstandng bracket 2S. A second plate 28 which issecured to casing I6 by a nut and bolt arrangement 3u is also providedwith a tapered extremity 32 that forms a continuation of bracket 26. Abearing rod 34 seen in Fig. 3 is supported between the outer end ofbracket 26 and an inner portion of the tapered end 24 of plate 20. Afine coil spring 3G is wound about bearing 34 and secured to the taperedportion 24 of plate 20 for purposes to be described hereinafter relativeto maintaining bearing 34 in a fixed position against axial rotation.

An armature 38 which is of rectangular configuration is supported onbearing 34 with its opposite ends extending horizontally with respect tothe horizontal axes of the casing, and the same is, as clearly shown,situated beneath the -central horizontal axes of the casing and adjacentthe lower portion of the casing. A first arcuate shaped permanent magnet4G, shown in dotted lines in Fig. 2, is supported within the base ofcasing I6 underneath a layer of insulation 4I and has its opposite polesspaced on either side of the ends of armature 38. A second arcuateshaped permanent magnet d2 is mounted within casing I6 and also has itsopposite poles indicated in Fig. 2 at 43 and ad spaced on opposite sidesof armature 38. While the device is effective when only one permanentmagnet is used, I have found that the armature is more stable when twomagnets are used because of the greater amount of magnetic force whichis applied by the combined action of magnets and 42. It is essential tostate at this point that the respective poles of the two magnets 49 and'42 on each side of the armature are of the same polarity so that Ibelieve the eifect is substantially the same as that which would beobtained if one magnet of stronger force were used in place of themagnets 4G and 42.

Also secured on bearing 23 is a needle et which is visible through anaperture 48 in a disk 5B as seen in Fig. 1. The disk 5S carries printedindicia thereon and shown as the letters N and S to indicate positiveand negative polarity.

' A rigid rod 52, formed of a low permeable ferrous material such assteel, extends through casing I2 and is rigidly secured to casing IB bya nut and bolt arrangement shown at 54 in Figs. 2 and 3. It is importantto point out that rod 52 is secured to casing IS immediately beneath thecenter of armature 38.

Referring now to Fig. 4 is shown the portion of an electric machine heredesignated `as a motor 55 having a rst eld winding 58 and diametricallyopposite thereto another field winding 6B which would presumably beoflopposite polarity from winding 58. The device 1nd1cated by generalreference numeral I0 is utilized to determine the polarity of poles 58and 6B by placing rod 52 within the magnetic field of each of the fieldwindings.

The operation of the device will now be explained. Referring to Fig. 4,the device I0 is shown in the manner in which it is applied to winding60 with the rod 52 in contact therewith. When rod 52 is brought into theproximity of the electromagnetic eld of winding 60 the magnetic flux isconducted through rod 52 to casing I6 adjacent the center of armature38. Armature 38 is normally situated between the magnetic poles d3 and44 of magnet 42 and similar poles of magnet l!) and, therefore, it iswithin the magnetic field of V,these magnets and will have positive andnegative poles at its opposite ends. The permanent magnets are notessential to the operation of the device, but they do tend to stabilizethe armature against uncontrolled wobbling movement. If the field ofwinding 60 is of positive polarity the armature 38 will rotate in acounterclockwise direction on bearing 26 and cause the needle 46 to movein the direction of the N indicia on disk 58; whereas if the polarity isopposite, the needle will be moved in the direction of the S indicia.The rod 52 merely acts as a conductor of the magnetic flux to a pointimmediately below the central axis of the armature. Of course, themagnetic effect of elds 5B and 6B are many times greater than magnets 40and 42 and will, therefore, instantly overcome the affect of thesemagnets. However, when rod 52 is taken away from fields 5B or 60, themagnets 40, d2 aided by the resilience of spring 36 will immediatelyreturn the armature to its normally horizontal position where it willagain form a path between the opposite poles of these magnets so that itwill not be affected by any residual magnetism resulting from use. Sincethe device would be used on fields of differing polarity, rod 52 beingformed of low permeable metal will not carry any considerable amount ofresidual magnetism. I have found that repeated use in fields of one typeof magnetism does not leave rod 52 carrying suicient residual magnetismto have any effect on armature 38.

My invention is not restricted to the single illustration but is definedin the terms of the appended claims.

I claim:

1. A device for indicating polarity of a magnetic field, comprising acasing, a linear magnetized armature centrally pivoted in the casing forrotative movement, at least one permanent magnet having portions ofopposite polarity on either side and spaced from the ends of thearmature, and a low permeable ferrous rod connected at one end to thecasing at one side of and in spaced relation to the centrally pivotedportion of the armature to conduct magnetic iiux from a magnetic fieldand thereby attract one end of the armature to indicate the polarity ofthe field by the direction of movement of the armature.

2. A device for indicating polarity of a magnetic field, comprising -acasing, a magnetized 4armature of linear configuration, a bearing rodwithin said casing at one side of the center thereof supporting saidarmature for rotative movement, resilient means connected to the bearingrod for resisting rotative movement of the armature, a permanent magnetcarried by the casing and having its opposite poles spaced from and inalignment with the opposite ends of the armature to stabilize thearmature against rotative movement, a flux conductor consisting of arigid ferrous rod of low permeability secured at 5 6 its inner end tothe casing on a, side thereof REFERENCES CITED nearest the armature andat right angles to the The following references are of record in theyrotative axis of the armature, said rod being adapted to conductmagnetic flux from an elecme of uns patent tromagentc field to theinterior of the casing to 5 UNITED STATES PATENTS attract one end of thearmature, and an indcat- Number Name Date ing means connected with thearmature and cO- 1,137,054c Everest June 13J 1916 operable with anindicia carried by the casing 1,353,421 Tear June 141J 1932 forindicating the polarity of the eld when one 1,949,521 Acosta Dm 19J 1933lend of the armature is attracted to the inner end 10 2,123,045 HoareJuly 5, 1938 of the rod.

ANDERS EINAR ANDERSSON.

